Rubber track

ABSTRACT

A rubber crawler has a structure in which connecting members are sequentially fitted onto wing portions adjacent to each other without using steel cords for resisting tensile force applied to the rubber crawler. Accordingly, the rubber crawler of the present invention has excellent characteristics in that breakage of steel cords due to the tensile force can be prevented, and torsion of the rubber crawler can be reduced.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rubber crawler mainly used forconstruction machines or civil engineering machines. More particularly,the present invention relates to a rubber crawler adopting a brand newstructure as a tensile reinforcing member.

2. Background Technology

Conventionally, steel cords are embedded in a rubber crawler in alongitudinal direction of the rubber crawler to operate as tensilereinforcing members resisting tensile force applied thereto. However, inordinary methods, when steel cords are formed in an endless manner,overlapped portions are formed between the steel cords. Due to this,there have been drawbacks in that a crawler operator can sensevibrations, and use of very high speed is impossible. Another thedrawback has also been pointed out that steel cords, which are used as atensile reinforcing member of a conventional rubber crawler, is easilybroken when excessive tensile force is applied thereto.

Japanese Patent Application (JP-A) Laid-pen No. 2000-313371 discloses arubber crawler having a structure in which steel cords are not used.However, since in the rubber crawler in this disclosure all the coremetals are of a type requiring assembly, problems are caused in that alot of time and labor is necessary for manufacturing the rubber crawlerand the rubber crawler does not exhibit excellent strength.Specifically, since considerably close attention must be paid especiallywhen core metals and tensile reinforcing members are assembled, workingefficiency is impaired. Further, since two bars are used at portionscorresponding to wing portions of the core metals, comparatively finematerials should be used. For this reason, it can be predicted thatproblems such as deterioration of strength may occur. Moreover, since aconnecting member for connecting these bars is structured to becomparatively easily elongated or the like, further improvements arerequired.

Accordingly, the present applicants are developing a rubber crawlerhaving a brand new structure in which conventional steel cords are notused and instead, metallic connecting members are used as tensilereinforcing members such that the metallic connecting members areconnected sequentially to wing portions of core metals adjacent to eachother.

In the brand new rubber crawler, holes for sequential connection areformed in advance on wing portions of core metals, and connectingmembers having hooks at both sides thereof corresponding with the holesare used. The hooks are engaged with the corresponding holes.Accordingly, all the core metals are connected to one another in anendless manner, and then embedded in rubber. A rubber crawler is thusformed. In this rubber crawler, since the rubber crawler can be formedendlessly without using steel cords as a tensile reinforcing member,vibration or the like is improved, and high tensile strength isexhibited. However, in actuality, further improvements are required.

In the present invention, a rubber crawler is further improved such thata core metal has a simpler structure and an engaging member has astronger structure.

SUMMARY OF THE INVENTION

The summary of the invention is a rubber crawler comprising an endlessrubber elastomer, core metals each including protruding portionsprotruding from an inner circumference of the rubber elastomer and apair of left-hand side and right-hand side wing portions embedded in therubber elastomer, and lugs formed at an outer circumference of therubber elastomer, wherein two connecting members are fitted onto each ofthe left-hand side and right-hand side wing portions of each core metalin the longitudinal direction of the rubber elastomer, such that theadjacent core metals are sequentially connected with each other.

The present invention is structured as described above. Steel cords,which are usually embedded as a tensile reinforcing member in a rubberelastomer in the longitudinal direction the0reof, are not embedded.Instead, wing portions of core metals are connected to one another byusing connecting members as a tensile reinforcing member. Further, twopairs of connecting members are fitted onto each pair of left-hand sideand right-hand-side wing portions at both ends of each core metal. Theconnecting members can exhibit higher strength than the conventionalsteel cords and excellent constraint force in resisting torsion of coremetals. Specifically, connecting members to which a tensile force isapplied and wing portions of core metals to which driving force fromsprockets is applied are embedded in a rubber elastomer so as to beflush with each other. Consequently, removal of core metals from arubber elastomer can be prevented.

Concerning the core metal, it is preferable that a portion of each ofthe left-hand side and right-hand-side wing portions onto which aconnecting member is fitted is formed into a substantially circularcross-sectional configuration for facilitating a rotation of theconnecting member therearound. Further, a side of the wing portion whichis not in contact with the connecting member can be formed into atrapezoidal shaped cross-sectional configuration, in order toeffectively prevent a swinging rotation of core metals. That is, thecross section of the wing portion at the side in contact with theconnecting member is formed into a substantially circular-shapedconfiguration, and that of the wing portion at the other side not incontact with the connecting member is formed into a trapezoidal-shapedconfiguration. Accordingly, when the rubber crawler is wound around anidler or a sprocket, a rotational movement of the connecting member isnot disturbed. Further, when a relative rotational force between coremetals and connecting members is large, or when a swinging rotationalforce in a direction opposite to the relative rotational force occurs,the inclining surfaces of the trapezoidal shape side that are notusually in contact with the connecting members, are brought into contactwith the connecting members to block further rotation between coremetals and connecting members. The inclining angle θ of an incliningsurface of the trapezoidal shape of the wing portions ranges from 5° to30°.

It is preferable that a tip end portion of the wing portion to be fittedinto the connecting member is a protruding portion whose cross-sectionalconfiguration is different from that of the remaining portion in orderto prevent the removal of the connecting member from the wing portionduring the assembly of the rubber crawler or after the rubber crawlerhas been completed. For this reason, for example, the tip end portion ofthe wing portion forms a protruding portion that extends in thelongitudinal direction or the thickness direction of the rubberelastomer.

Expanded portions can be provided at the outer side of each protrudingportion of each core metal so as to extend along the longitudinaldirection of the rubber elastomer. Such expanded portions are expandedon at least one side in the longitudinal direction of the rubberelastomer, and are generally formed in a flat shape. Since the expandedportions are partially or entirely embedded in the rubber elastomer, thewing portion having the substantially circular or wing-shapedcross-sectional configuration can be prevented from being easily rotatedin the rubber elastomer. The expanded portions can be formed either atimmediate outer sides of the protruding portions, at the midpoints ofthe wing portions toward the connecting members, or at the tip endportions of the wing portions. When flat expanded portions are formedimmediately at both outer sides of the protruding portions, the expandedportions are exposed (protruded) from the rubber elastomer and used asrail portions during wheel running. The aforementioned structuralfeatures of the core metals are shaped by the core metals of otheraspects of the present invention described below.

It is most preferable that the connecting member is formed by a metal.However, from the standpoints of the dimensions of a rubber crawler or arelationship between the connecting member and a tensile force, aplastic product can be used. Engaging portions, each having asubstantially circular cross-sectional configuration, are formed at bothends of the connecting member, whereby the engaging portions aresequentially engaged with the wing portions of the core metals. Then,two pairs of connecting members are used for each pair of the left-handside and right-hand side wing portions of the core metal, to dispersethe tensile force and resist torsion of the core metals. The engagingportions are structured such that they are inwardly open at one side, orinwardly open at the other side, or closed endlessly in the longitudinaldirection of the rubber elastomer, or the like. Among these, an engagingportion having the closed and endless structure is the strongest.Further, a flat portion may be formed at one side of the connectingmember and embedded in the rubber elastomer so as to face wheels, andthen exposed from the rubber elastomer surface, to form rail portions onwhich wheels travel. Connecting members can be formed into otherconfigurations as will be described later with reference to thedrawings. A variety of arrangements of the connecting members can beconsidered, and examples thereof include a symmetric arrangement, anon-symmetric arrangement, a staggered arrangement, an arrangement usinga second connecting member, or an arrangement in combination thereof.

The invention using a second connecting member is a rubber crawlercomprising an endless rubber elastomer, core metals including protrudingportions protruding from an inner circumference of the rubber elastomerand pairs of left-hand side and right-hand side wing portions embeddedin the rubber elastomer on either side thereof, and lugs formed at anouter circumference of the rubber elastomer, wherein fitting holes areformed at both ends of each of the wing portions, and tip end portionsof a second connecting member which is bent into a substantially U shapeare fitted into the fitting holes of the wing portions of each of thecore metals adjacent to each other, such that all the core metals aresequentially connected to one another.

Further, while there is a case in which wheels travel on innercircumferential surfaces of the rubber crawler, there is also a case inwhich rails are provided at the wing portions at both outer sides of theprotruding portions of the core metals. Alternately, the cross-sectionalconfiguration of a wing portion of a core metal can be changed or aprotruding portion can be formed in order to prevent removal of theconnecting member from the wing portion. Any structure for a core metalcan be adopted.

The wing portions of the core metals need not be one single piece andcan be branched like a stonometer to form a fork shape, and theconnecting members can be fitted onto the branch portions of the forkshapes. In this case, the wing portions becomes flat as a whole, andunwanted rotation or swinging rotation of the wing portions duringrunning of wheels can be prevented. More specifically, the wing portionsare branched into a two-forked portion or a three-forked portion ontowhich end portions of a connecting portion can be fitted.

The present invention can provide a rubber crawler having theabove-described structure, in which steel cords which have beenconventionally used is rendered unnecessary, which can exhibit excellentstrength as compared to that in a conventional rubber crawler. Further,the assembly of the rubber crawler can be simplified and secured, andsince the wing portions of the core metals and the connecting membersare embedded in the rubber elastomer to be flush with each other, thephenomenon of torsion and the occurrence of removal of the core metalsfrom the rubber elastomer or the like can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an inner circumferential surface side of arubber crawler of a first example according to one embodiment of thepresent invention.

FIG. 2 is a side view of FIG. 1.

FIG. 3 is a plan view of an inner circumferential surface side of arubber crawler according to another embodiment of the present invention.

FIG. 4 is a side view of FIG. 3.

FIG. 5 is a cross-sectional view taken along a line A-A.

FIG. 6 is a cross-sectional view taken along a line B-B.

FIG. 7 is a cross-sectional view taken along a line C<.

FIG. 8 is a plan view of an inner circumferential surface side of arubber crawler in which recesses are formed at predetermined positions.

FIG. 9 is a plan view of a first example of an outer circumferentialside structure of a rubber crawler.

FIG. 10 is a plan view of a second example of an outer circumferentialside structure of a rubber crawler.

FIG. 11 is a plan view of a third example of an outer circumferentialside structure of a rubber crawler.

FIG. 12 is a perspective view of a first example of a connecting member.

FIG. 13 is a perspective view of a second example of a connectingmember.

FIG. 14 is a perspective view of a third example of a connecting member.

FIG. 15 is a perspective view of a fourth example of a connectingmember.

FIG. 16 is a perspective view of a fifth example of a connecting member.

FIG. 17 is a cross-sectional view showing a relationship betweenconnecting members of FIG. 15 and core metals.

FIG. 18 is a plan view of a relationship between wing portions ofanother example, of a core metal, and connecting members.

FIG. 19 is an inner circumferential side plan view showing yet anotherexample of a rubber crawler.

FIG. 20 is a side view of FIG. 19.

FIG. 21 is yet another side view of FIG. 20.

FIGS. 22A through 22D are inner circumferential side plan views of otherexamples of core metals.

FIG. 23 is an inner circumferential side plan view of yet anotherexample of a core metal.

FIG. 24 is a plan view of a sixth example of a connecting member.

FIG. 25 is a side view of the connecting member of FIG. 24.

FIG. 26 is a plan view of a relationship between core metals and theconnecting members shown in FIGS. 24 and 25.

FIG. 27 is a plan view of a relationship between the connecting memberand core metals having two-forked wing portions.

FIG. 28 is a cross-sectional view taken along line D-D of FIG. 27.

FIG. 29 is a plan view of a relationship between the connecting memberand core metals having three-forked wing portions.

FIG. 30 is a plan view of a relationship between core metals and secondconnecting members used as the connecting members.

FIG. 31 is a side view of FIG. 30.

FIG. 32 is a cross-sectional view taken along line E-E of FIG. 30.

FIG. 33 is a partial view of a relationship between the secondconnecting members as the connecting members and core metals accordingto another example.

FIG. 34 is a partial view of a relationship between the secondconnecting members as the connecting members and core metals accordingto yet another example.

FIG. 35 is a plan view of still another example of a relationshipbetween wing portions of core metals, and connecting members.

EMBODIMENTS

Hereinafter, with reference to the drawings, embodiments of the presentinvention will be explained in more detail.

FIG. 1 is a plan view illustrating an inner circumferential surface sideof a rubber crawler of a first example according to one embodiment ofthe present invention, and FIG. 2 is a side view thereof. FIG. 3 is aninner circumferential side plan view illustrating a rubber crawler of asecond example according to the one embodiment of the present invention,and FIG. 4 is a side view thereof. FIG. 5 is a cross-sectional viewtaken along a line A-A, FIG. 6 is a cross-sectional view taken along aline B-B, and FIG. 7 is a cross-sectional view taken along a line C-C.

In these figures, the reference numeral 1 refers to a rubber elastomerthat is a base body constituting a rubber crawler. In FIGS. 1 and 3, therubber elastomer 1 is connected endlessly in the top-bottom direction ofthe respective paper surfaces of the drawings. The reference numeral 2refers to a core metal. The core metal 2 comprises a pair of protrudingportions 3 and 4 that are formed so as to protrude from an innercircumferential surface of the rubber elastomer 1, and wing portions 5and 6 that are formed at a left-hand side and at a right-hand side ofthe core metal 2. The wing portions 5 and 6, each of which is formedwith a substantially circular cross-sectional shape, are embedded in therubber elastomer 1. Further, in the example of FIG. 3, expanded portions(flat portions) 7 and 7 are formed respectively on the outer side of thepair of the protruding portions 3 and 4. The flat portions 7 and 7comprise exposed portions that are exposed on the inner circumferentialsurface of the rubber elastomer 1 and embedded portions that areembedded in the rubber elastomer 1, and prevent the core metal 2 fromswinging in the longitudinal direction or in the transverse direction ofthe core metal 2. The surfaces of the flat portions 7 and 7 are railportions on which wheels travel.

Connecting members 10 in two rows (10 a, 10 b and 10 c, 10 d) arefittingly arranged in a staggered form in the longitudinal directiononto the wing portions 5 and 6 of the core metals 2 adjacent to oneanother, whereby all the core metals 2 are connected to one another.FIG. 1 shows a symmetric arrangement of the connecting members 10.Specifically, the connecting members (10 a, 10 b) are fitted onto thewing portions 5 in a staggered form in the longitudinal direction,whereby the core metals 2 are connected to one another. Similarly to theconnecting members (10 a, 10 b), the connecting members (10 c, 10 d) arealso fitted onto the wing portions 6. Accordingly, the wing portions 5and 6 on the left and the right are connected to one another to form asymmetric arrangement. Of course, while not shown, the connectingportions 10 can form an asymmetric arrangement on the left and theright.

When the rubber crawler is entrained around an idler or a sprocket,since the connecting members are formed to have rigid bodies,deformation of portions with the connecting members embedded therein iscomparatively low, while deformation of portions without the connectingmembers embedded therein is unavoidably high. Such difference indeformation is especially conspicous between the connecting members anda portion of the rubber elastomer which completely lacks the connectionmember in the transverse direction thereof. Consequently, torsion due torepetitive tensile and compressive deformation is focused on the portionof the rubber elastomer which completely lacks the connection member inthe transverse direction thereof.

As shown in FIG. 8, for example, recesses B1 through B4 may be formed atan inner circumferential side and/or at an outer circumferential side ofthe rubber elastomer 1 at the portions of the rubber elastomer whichcompletely lack the connection members in the transverse directionthereof. Accordingly, the focusing of torsion due to repetitive tensileand compressive deformation on a particular portions can be preventedthus making it possible to prevent deterioration of the rubber elastomer1 and increase the durability of the rubber crawler.

With regard to a rubber crawler, if the rubber crawler is distorted orit passes over protruding portions on the running surface, cracks or thelike can be easily formed on the rubber elastomer 1 covering theconnecting members 10 b and 10 d at both left and right edge sides ofthe rubber elastomer 1. In consideration of this problem, as shown inFIG. 9, in some cases it is necessary to form lugs 8 a and 8 b forcovering the connecting members 10 b and 10 d. In this structure, thethickness of the rubber at the outer circumferential side of connectingmembers 10 b and 10 d is significantly large (this thick portion withlugs will be referred to a “thick rubber portion” hereinafter). Whenprotrusions collide with the thick rubber portion, external forceapplied thereto is damped and absorbed by the rubber elastomer 1 (thelugs 8 a and 8 b), and the external force applied on the connectingmembers is significantly reduced. Consequently, occurrence of cracks onthe rubber elastomer can be reduced thus making it possible to increasethe durability of the rubber crawler.

FIG. 10 is a plan view of a modified example of FIG. 9. In this example,large thick portions 8 c are formed at the outer circumferential surfaceof the connecting members 10 a and 10 c which are not covered with thelugs 8 a and 8 b in order to increase the durability of the rubbercrawler 1. The thickness of the large thickness portion 8 c can beappropriately chosen in accordance with the dimensions or thepredetermined conditions of use for the rubber crawler 1.

As shown in FIG. 11, there is a case in which the connecting members (10a through 10 d) are fitted onto the wing portions 5 and 6 of the coremetals 2 in a symmetric arrangement around the central longitudinalaxis. In this case, the aforementioned lugs 8 a and 8 b can be usedunchanged. However, for example, protruding portions 8 d can be provideddirectly beneath the running surface of unillustrated wheels in order toprevent vibrations.

FIG. 12 is a perspective view showing a first example of the connectingmember 10 which is formed into a flat annular shape and in whichengaging portions 11 a and 11 b, each having a substantially circularinner end, are formed at both ends thereof.

FIG. 13 shows a second example of the connecting member 10 in which theengaging portions 11 a and 11 b are opened inwardly at one side. FIG. 14shows a third example of the connecting member 10 in which the engagingportions 11 a and 11 b are opened inwardly in directions opposite toeach other.

FIG. 15 is a side view of a fourth example of the connecting member 10in which one side portion of the connecting member 10 (generally,corresponding to the inner circumferential side portion of the rubbercrawler) has a straight portion 10 x, the other side portion(ordinarily, corresponding to the outer circumferential side portion ofthe rubber crawler) has a recess 10 y at the center thereof, and theengaging portions 11 a and 11 b, each having a circular innercircumferential surface, are formed at both ends of the connectingmember 10. FIG. 16 is a side view of a fifth example of the connectingmember 10 which is formed in a substantially optical shape.

When the connecting members 10 as shown in FIGS. 15 and 16 are used fora rubber crawler, the recess 10 y at the center thereof is filled with arubber elastomer, and thus external force from the running surfaceduring crawler running can be damped and absorbed by a rubber elastomerlayer having increased volume, the force applied to the connectingmembers is decreased, and occurrence of cracks on the rubber elastomercan be reduced. As a result, the durability of the rubber crawler can beenhanced.

FIG. 17 shows a cross-sectional view of a main portion of the rubbercrawler when the connecting member 10 of FIG. 15 is used. The connectingmember 10 is embedded in the rubber elastomer 1. The curvedly-recessedsurface 10 y is formed at the outer circumferencial surface side of theconnecting member 10. The connecting member 10 at the outercircumferential surface side thereof is thus filled with a larger amountof the rubber elastomer 1 (larger by the amount of the recess 10 y) thanthe case with the connecting member 10 without the recess 10 y. Incontrast, when the curvedly-recessed surface 10 y is not formed at theconnecting member 10 at the outer circumferential surface side of therubber elastomer, the entire thickness of the rubber elastomer 1 isquite small (i.e., the rubber portion 1 b). It can be assumed thatdamping effects will be deteriorated when the thin rubber portion (1 b)collides with protrusions on the running surface when the rubber crawleris running, and cracks are easily formed on the rubber elastomer 1.However, in the structure shown in FIG. 17, since the curved-recessedsurface 10 y is provided at the connecting member 10 at the outercircumferential side thereof, the connecting member 10 at the outercircumferential surface side thereof is filled or covered with a largeramount (thick rubber portion 1 a) of the rubber elastomer 1 (larger bythe amount of the recess 10 y) than the case with the connecting member10 without the recess 10 y. Accordingly, when protrusions on the runningsurface on which the crawler travels collide with the thick rubberportion 1 a, external force applied thereto is well damped and absorbedby the rubber elastomer 1, and the external force applied to theconnecting member 10 is significantly reduced. Consequently, theformation of cracks on the rubber elastomer 1 can be reduced thus makingit possible to increase the durability of the rubber crawler.

A method for forming through holes in the connecting members 10 can beused for improving adhesiveness or attaching property thereof. In theexample of FIG. 12, through holes 11 c are formed on the connectingmember 10. In this structure, a reliable adhesiveness can be obtainedbecause rubber is introduced into the inner side of the connectingmember 10 by way of the through holes 11 c during the vulcanization. Ofcourse, through holes 11 c can be applied to the various types ofconnecting member 10.

Next, further examples of the wing portions 5 and 6 of the core metal 2will be described. FIG. 18 shows a cross-sectional view similar to FIG.5. In this example, the structure of the core metal 2 can be improved toprevent vibrating rotation of the core metal 2, improving ridingcomfort, preventing removal of wheels, and improving durability. Namely,the wing portion 5 at a surface that is contacted with the connectingmember 10 is formed by a substantially circular shape 9 a, while asurface thereof that is not contacted with the connecting member 10 isformed by a tapered trapezoidal shape 9 b continuous with the circularshape 9 a. The trapezoidal shape 9 b has inclining surfaces 9 c and 9 dthat are inclined at an outer circumferential side inclining angle θ 1and an inner circumferential side inclining angle θ2, respectively. Theouter circumferential side inclining angle θ1 is set substantially equalto a maximum inclining angle formed when the rubber crawler is entrainedaround an idler or a sprocket. The inner circumferential side incliningangle θ2 is set as a tolerable play angle for allowing the swinging ofthe core metal 2. The inclining angle θ1, which changes in accordancewith a radius of the idler or the sprocket around which the rubbercrawler is wound, ranges from about 5° to about 30°, and the incliningangle θ2 is equal to or smaller than the inclining angle θ1 (generally,θ2 ranges from about 5° to 20°).

When the connecting members 10 are fitted with the wing portions 5 and6, it is necessary to fit the connecting members 10 onto the wingportions 5 and 6 in a predetermined position. Accordingly, it isfavorable to provide the wing portions 5 and 6 with steps that willfacilitate assembly. For this reason, as shown in the example of thecore metal 2 in FIG. 19, a ring-shaped convex step 12 may be formed ateach of the wing portions 5 and 6.

It is necessary that the fitting of the connecting members 10 onto thewing portions 5 and 6 of the core metal 2 must be reliably maintainedduring assembly, after being embedded in the rubber elastomer 1, andduring practical use for running. For this reason, as shown in FIG. 19,it is preferable that protruding portions 13 are formed at therespective tip end portions of the wing portions 5 and 6. FIG. 20 isanother example of the core metal 2 in which the protruding portion 13is formed to extend in a longitudinal direction of the rubber elastomer,and FIG. 21 is yet another example of the core metal 2 in which theprotruding portion 13 is formed to extend in a thickness direction ofthe rubber elastomer.

As described above, each of the wing portions 5 and 6 of the core metal2 is formed into a substantially circular cross-sectional configurationthat can easily rotate in the rubber elastomer 1. Therefore, in somecases, it is necessary to form expanded portions respectively at thewing portions 5 and 6, and then embed them into the rubber elastomer 1to thereby suppress rotations of the wing portions 5 and 6. As anexample of such, description has been made with respect to FIG. 3 of theexpanded portions (flat portions) 7 serving as rails on which wheelstravel. However, the structure of the expanded portions is not limitedto this, and instead, as shown in FIGS. 22A through 22D and FIG. 23, anexpanded portion (ordinarily, flat portion) 7 a may be formed at thecenter of each of the wing portions 5 and 6 or at the tip end thereof soas to extend in a longitudinal direction of the rubber elastomer 1, andbe entirely or partially embedded in the rubber elastomer 1 thus makingit possible to prevent the drawback that the wing portions 5 and 6 arerotated within the rubber elastomer 1. Further, the expanded portion 7 acan be formed at an arbitrary position at each of the wing portions 5and 6. For example, the expanded portion 7 a can be protruded into eachof the wing portions and 6. An expanded portion 7 as can be formed atthe center, in the transverse direction, of the wing portions 5 and 6,optionally having a neck portion 7 b at the center, in the verticaldirection, of the wing portions 5 and 6. Of course, an expanded portionformed at the tip end portion of each wing portion is also acceptable.Recesses or holes can be formed on the expanded portion (flat portion) 7a or 7 as in order to provide the rubber elastomer 1 with an anchorfunction.

FIG. 24 is a plan view of an improved example of the connecting member10, and FIG. 25 is a side view thereof. In the example, a flat surface10 f is provided at one end of a connecting member 10 e so as toprotrude therefrom. The flat portion 10 f can be used as theaforementioned expanding member or it can be used unchanged as a railportion on which wheels can travel.

FIG. 26 is a plan view of a combination of the connecting members 10 eand the core metals 2. Here, instead of the connecting members 10 a and10 c, the connecting members 10 e having the flat portions 10 f aredisposed. As can be seen from this figure, since the flat portions 10 fare used as rails on which wheels travel, the running road surface canbe kept as long as possible, and reduction of vibrations can be ensured.In this structure, needless to say, there are many advantages in thatthe formation of rail portions on the core metals 2 themselves becomesunnecessary, the configuration of the core metals 2 can be simplified,the core metals 2 can be manufactured inexpensively, the core metals 2can be made compact, and the core metals 2 can be handled more easily.

FIG. 27 is a plan view of an inner circumferential side of the rubbercrawler 1 in which two-forked wing portions (5 a and 5 b, 6 a and 6 b)are formed, showing only the core metals 2 and connecting members 10 g.FIG. 28 is a cross-sectional view taken along line D-D of FIG. 27.

In these figures, the wing portions 5 a and 5 b, and 6 a and 6 b areprovided on either side of the rubber elastomer 1, and are embeddedtherein. Endless and flat-shaped connecting members 10 g aresequentially fitted onto the wing portions (5 a and 5 b, and 6 a and 6b). Accordingly, the core metals 2 and the connecting members 10 g arecontinuously, i.e., endlessly arranged in the top-bottom direction ofthe paper surface of the drawing, and are embedded in the rubberelastomer 1 (not shown) in a state in which the connecting members 10 gare fitted onto the wing portions (5 a and 5 b, and 6 a and 6 b).

The wing portions (5 a and 5 b, 6 a and 6 b), each of which is formedinto a substantially circular sectional configuration which is slightlysmaller than the semi-circular sectional configuration of each of thefitting surfaces (11 a and 11 b) of the connecting members 10 g, arefitted into the connecting members 10 g, whereby a smooth rotation ofthe rubber crawler is enabled. The smooth rotation can providecharacteristics of reducing resistance to winding exhibited by therubber crawler when the rubber crawler is wound around an idler or asprocket.

Although the wing portions (5 a and 5 b, 6 a and 6 b) themselves have acircular cross-sectional configuration, they are embedded in a doubleline rubber elastomer. This is essentially similar to a case in which awing portion has a large width, and vibrating rotation of the coremetals 2 can thus be reduced to a great extent. Further, protrudingportions 5 c and 6 c are formed at the wing portions (5 a and 5 b, 6 aand 6 b) in order to position and the connecting members 10 g in placeand keep them aligned. Of course, these protruding portions 5 c and 6 ccan be applied to various types of wing portions.

FIG. 29 is a plan view of an example of an inner circumferential side ofthe rubber crawler 1 in which a three-forked wing portion is formed. Inthis case, a third wing portion 50 is formed between the wing portions 5a and 5 b and a third wing portion 60 is formed between the wingportions 6 a and 6 b. In addition, each of the third portions 50 and 60is formed into a flat cross-sectional configuration and also is long ina transverse direction. The entire wing portion (5 a and 5 b and 50 or 6a and 6 b and 60) can exhibit almost the same effect as a wing portionhaving a flat portion as wide as the wing portions 5 a and 5 b plus thethird wing portion 50 would, whereby vibrating rotation of the coremetal 2 can further be reduced.

FIG. 30 is a plan view of an inner circumferential side of a rubbercrawler in which core metals are connected to one another by using asecond connecting member 10 h whose structure is different from those inthe above-description, FIG. 31 is a side view thereof, and FIG. 32 is across sectional view taken along line E-E.

The above-described endless and flat connecting members 10 are shown.Substantially semicircular fitting portions are formed at both ends ofthe connecting member 10. A pair of the fitting portions are fitted ontothe corresponding wing portions 5 and 6 of two core metals, as shown inFIG. 30. On the other hand, the second connecting member 10 h is formedinto a longitudinal U-shape, and each of bent portions 10 h ₁ and 10 h ₂at both sides of the second connecting member 10 h is formed into acylindrical shape. The bent portions 10 h ₁ and 10 h ₂ at both sides ofthe second connecting member 10 h are fitted into the correspondingholes 50 and 60 formed at the tip end portions of the wing portions 5and 6 of the core metals 2, whereby the entire core metals 2 can beconnected to one another. As described above, the rubber crawler of thepresent invention is formed by embedding the core metals 2 and theconnecting members 10 and 10 h in the rubber crawler (not shown).Further, these two types of the connecting members can be fitted ontothe wing portions in a symmetric form or in a staggered form.

In a structure in which sets of two different types of connectingmembers are fitted onto both left-hand side and right-hand side portionsof the wing portions, there may be a case in which not all of the wingportions are long enough for such an arrangement, that is, some of thewing portions may not be long enough to accommodate two connectingmembers therein. Further, in the rubber crawler using a conventionaltensile reinforcing member, the rubber crawler may be distorted upon areceipt of external force and/or edge breakage may occur upon a receiptof shearing force, whereby durability is deteriorated.

In view of the aforementioned problem, the core metals 2 can besequentially connected to one another by using the first connectingmembers 10 for connecting wing portions themselves and the secondconnecting members 10 h for connecting only tip end portions of the wingportions. Accordingly, when the length of a wing portion isinsufficient, a connecting member with sufficient strength can be fittedonto the wing portion. Since the second connecting member 10 h can befitted onto the wing portion from the transverse direction thereof, theconnection can be simplified. More specifically, since the secondconnecting member 10 h and the tip end portions of the wing portions 5and 6 are fitted to each other, portions with high rigidity can beformed in the vicinities of both edge ends of the rubber crawler.Consequently, the occurrence of edge breakage can be reduced. Moreover,the second connecting members 10 h also prevent the first connectingmembers from being removed from either end of the wing portions, withaligning the wing portions.

The second connecting member 10 h is inserted into a pair of holes whichare formed at outermost tip end portions of each wing portion. However,depending on the applications, the second connecting member 10 h can beinserted into a pair of holes which are formed at innermost tip endportions of each wing portion, as shown in FIG. 33. When the secondconnecting member 10 h is thus employed for the outermost ends or theinnermost ends of the wing portion, there is a case in which theconnecting member 10 is rendered unnecessary.

Furthermore, each bent portions 10 h ₁ and 10 h ₂ can be sequentiallyinserted into two holes or two elongated holes that are formed at bothtip end portions or both inner ends of the wing portions. Accordingly,this provides the present invention with new characteristics in that therubber crawler can be constituted without using the first connectingmember 10.

FIG. 34 shows another example of the fitting structure between thesecond connecting member 10 h and the wing portion 6 in which a holeportion 10 h ₀ formed on the second connecting member 10 h can be fittedonto the wing portion 6.

FIG. 35 shows yet another example of a connecting member 10 i in whichone end portion of an engaging portion 10 i ₁ is two-forked, and one endportion of another engaging portion 10 i ₂ is disposed inside thetwo-forked end portion of the engaging portion 10 i ₁ in a nestingstate. Engaging portion 11 c or 1 d can be formed into any of theconfigurations of the examples described above.

EFFECTS OF THE INVENTION

Since the present invention is structured as described above, anexcellent rubber crawler can be obtained in which the embedding of steelcords for a tensile reinforcement is rendered unnecessary, strength of atensile reinforcing member is increased, and torsion of core metals canbe reduced.

1. A rubber crawler comprising: an endless rubber elastomer; core metalsincluding protruding portions protruding from an inner circumference ofthe rubber elastomer and pairs of left-hand side and right-hand sidewing portions embedded in the rubber elastomer; and lugs formed at anouter circumference side of the rubber elastomer, wherein two connectingmembers are fitted onto each of the left-hand side and right-hand sidewing portions of each core metal in the longitudinal direction of therubber elastomer, such that the adjacent core metals are sequentiallyconnected with each other.
 2. The rubber crawler of claim 1, whereinrails on which wheels travel are provided at outer sides of theprotruding portions of the core metals, and the wing portions onto whichthe connecting members are fitted are formed at further outer sides ofthe rails.
 3. The rubber crawler of claim 1, wherein a portion of thewing portions onto which the connecting members are fitted is formedwith a substantially circular cross-sectional configuration.
 4. Therubber crawler of claim 1, wherein a tip end portion of the wingportions is a protruding portion which is formed with a cross-sectionalconfiguration different from that of the portion of the wing portionsonto which the connecting members are fitted.
 5. The rubber crawler ofclaim 4, wherein a protruding portion extending in the longitudinaldirection of the rubber elastomer is formed at the tip end portion ofthe wing portions.
 6. The rubber crawler of claim 4, wherein aprotruding portion extending in the thickness direction of the rubberelastomer is formed at the tip end portion of the wing portions.
 7. Therubber crawler of claim 1, wherein engaging portions, each having asubstantially circular inner circumferential surface, are formed at bothends of the connecting members.
 8. The rubber crawler of claim 1,wherein a flat portion is provided at one side of the connectingmembers, and is exposed at an inner circumferential surface of therubber elastomer to form a rail on which wheels travel.
 9. The rubbercrawler of claim 1, wherein, as seen from a side view, a straightportion is formed at an inner circumferential side of the connectingmembers, an intermediate portion of the connecting members at an outercircumferential side thereof is recessed toward the inner circumferencethereof, and engaging portions, each having a substantially circularinner surface, are formed at both ends of the connecting members. 10.The rubber crawler of claim 1, wherein the connecting members arearranged in a staggered form in the longitudinal direction of the rubberelastomer.
 11. The rubber crawler of claim 10, wherein the connectingmembers are arranged in a staggered form in the longitudinal directionof the rubber elastomer, and lugs for substantially covering theconnecting members at end sides in a transverse direction of the rubberelastomer are formed.
 12. The rubber crawler of claim 10, wherein setsof the connecting members fitted onto the left-hand side and right-handside wing portions of the core metals are arranged symmetrically in atransverse direction of the rubber elastomer.
 13. The rubber crawler ofclaim 10, wherein sets of the connecting members fitted onto theleft-hand side and right-hand side wing portions of the core metals arearranged asymmetrically in a transverse direction of the rubberelastomer.
 14. The rubber crawler of claim 1, wherein the cross sectionof the wing portions at a side in contact with the connecting members isformed into a substantially circular-shaped configuration, and the crosssection of the wing portions at another side not in contact with theconnecting members is formed into an trapezoidal configuration.
 15. Therubber crawler of claim 14, wherein an inclination angle θ of aninclining surface of the trapezoidal section ranges from 5° to 30°. 16.The rubber crawler of claim 1, wherein expanded portions are formed atboth outer sides of the protruding portions of each core metal, and thewing portions, the connecting members and the expanded portions areembedded in the rubber elastomer or embedded therein with portionsthereof being exposed.
 17. The rubber crawler of claim 16, wherein theexpanded portions are provided in the vicinities of left-hand side andright-hand side outer sides of the protruding portions of the coremetals.
 18. The rubber crawler of claim 16, wherein the expandedportions are provided at the midpoints of the wing portions toward theconnecting members.
 19. The rubber crawler of claim 16, wherein theexpanded portions are provided at tip ends of the wing portions.
 20. Arubber crawler comprising: an endless rubber elastomer; core metalsincluding protruding portions protruding from an inner circumference ofthe rubber elastomer and pairs of left-hand side and right-hand sidewing portions embedded in the rubber elastomer; and lugs formed at anouter circumference of the rubber elastomer, wherein fitting holes areformed at both ends of each of the wing portions, and tip end portionsof a second connecting member which is bent into a substantially U shapeare fitted into the fitting holes of the wing portions of each of thecore metals adjacent to each other, such that all the core metals aresequentially connected to one another.
 21. The rubber crawler accordingto claim 20, wherein the fitting holes are formed on the tip endsurfaces of the wing portions.
 22. The rubber crawler according to claim20, wherein the fitting holes are formed so as to face sprocket engagingholes of the wing portions.
 23. The rubber crawler according to claim20, wherein the fitting holes formed at the ends of the wing portionsare elongated holes into which the bent tip portions of the secondconnecting member are fitted at the same time.
 24. The rubber crawleraccording to claim 20, wherein the fitting holes formed at the ends ofthe wing portion are elongated holes into which the bent tip portions ofthe second connecting member are fitted separately.
 25. The rubbercrawler according to claim 20, wherein the bent tip portions of thesecond connecting member is columnar.
 26. The rubber crawler accordingto claim 20, wherein first connecting members are alternately fittedonto the wing portions of the core metals adjacent to each other, andthe second connecting members are mounted on the tip end portions of thewing portions onto which the first connecting members are not fitted,whereby all the core metals are sequentially connected to one another.27. A rubber crawler comprising: an endless rubber elastomer; coremetals including protruding portions protruding from an innercircumference of the rubber elastomer and pairs of left-hand side andright-hand side wing portions embedded in the rubber elastomer; lugsformed at an outer circumference of the rubber elastomer; and connectingmembers which are sequentially fitted, in a longitudinal direction ofthe rubber elastomer, onto the pairs of the left-hand side andright-hand side wing portions of the core metals which are arrangedadjacent to each other, such that all the core metals are connected toone another, wherein the wing portions are branched in the longitudinaldirection to form a two-forked portion having branch portions, each ofwhich is formed into a substantially circular cross-sectionalconfiguration and onto which the connecting members are fitted.
 28. Therubber crawler according to claim 27, wherein a third wing portion isinterposed between the branch portions of the two-forked portion. 29.The rubber crawler according to claim 28, wherein the third wing portioninterposed between the branch portions of the two-forked portion is flatin the longitudinal direction of the rubber elastomer.
 30. The rubbercrawler according to claim 28, wherein the third wing portion is longerthan the branch portions of the two-forked portion.
 31. The rubbercrawler according to claim 27, wherein protruding portions are formed atthe branch portions so as to face each other, the protruding portionsaligning the connecting members fitted to the branch portions in placein the transverse direction.